1. Field of the Invention
The present invention relates to a method of manufacturing a ceramic honeycomb structure with some cell ends closed and a through hole forming device used for the process of manufacture.
2. Description of the Related Art
A filter structure for trapping the particulates in the exhaust gas of an automotive vehicle, for example, assumes the form of a ceramic honeycomb structure 8 in which a multiplicity of cells 88 are defined by partitioning walls 81 and alternate ones of the cells 88 have the ends thereof closed with a closing material 830, as shown in FIGS. 14(a) and 14(b).
In manufacturing the ceramic honeycomb structure 8 having this special form, as shown in FIG. 15, a body 86 of a honeycomb structure with the two ends of each of the cells 88 open is fabricated and a closing material 830 (FIGS. 14(a) and 14(b)) is filled to close the open cell ends.
In the prior art, the process for closing the cell ends of the honeycomb structure body 86 is performed in the following manner.
As shown in FIGS. 15(a) and 15(b), an end surface of the honeycomb structure body 86 is covered with a wax sheet 91 and pressed to fill the wax 90 in the ends of the cells 88. Then, as shown in FIG. 15(c), the wax 90 filled in the cell ends to be closed is scraped out manually using a jig or the like thereby to form open cell ends 880.
The honeycomb structure body 86 is dipped into a slurry 60 containing an end closing material with the end surface of the body 86 filled with the wax 90 down, so that the slurry 60 is caused to enter the cell ends 88 lacking the wax 90. The slurry 60 is then dried or baked while at the same time removing the wax 90. In the case where the closed portion 83 is formed at the two end surfaces of the honeycomb structure, the aforementioned process up to the dipping into the slurry is repeated for the other end surface.
The conventional method of manufacturing a honeycomb structure described above poses the following problems.
Specifically, as described above, the process for closing the cell ends includes a multiplicity of complicated steps of removing the filled in wax 90. With the decrease in the thickness of the honeycomb structure and the cell size, on the other hand, it has become increasingly difficult to manually remove the wax 90, thereby further adding to the number of steps.
Also, in the case where the closed portion 83 is formed at the two end surfaces of the honeycomb structure body 86, the process (masking) for filling the wax 90 and removing a part thereof is required for each of the two end surfaces. This is one of the processes for which improvement is required most of all the processes of manufacturing a honeycomb structure.